The present invention relates to a method of producing a ferrule and a ferrule.
A ferrule 1 for a multi-fiber connector as shown in FIG. 12, for example, has a flange 1b of a synthetic resin at the rear portion of a body 1a whose rear portion from nearly the center has a cylindrical shape, and an opening 1c formed in the center of the body 1a. The ferrule 1 has two pin holes 1d formed in the lengthwise direction for insertion of guide pins and a plurality of fiber holes 1e for insertion of optical fibers formed between the two pinholes 1d. 
The ferrule 1 is assembled into an optical connector by inserting optical fibers into the fiber holes 1e from back, injecting an adhesive through the opening 1e to adhere the optical fibers into the fiber holes 1e, and sealing the opening 1c with the adhesive.
Accordingly, it is an object of the present invention to provide a ferrule producing method and a ferrule which can prevent fiber holes from being bent at the time of molding and can form the fiber holes accurately.
To achieve the objective, according to the present invention, a method of producing a ferrule having a plurality of fiber holes for insertion of optical fibers formed between two pin holes for insertion of guide pins, which comprises a step of injecting a synthetic resin in a mold for forming the ferrule while holding a plurality of pins with a Young""s modulus of (22 to 59)xc3x971010N/m2 for forming the fiber holes at two points separated by a distance of 1.5 to 4mm in a lengthwise direction of the pins.
To achieve the object, a first ferrule according to the present invention, produced by the method as described above, comprises pin holes for insertion of guide pins; a plurality of fiber holes for insertion of optical fibers, formed between the pin holes; and an opening which communicates with the plurality of fiber holes and through which an adhesive for securely adhering the optical fibers in the fiber holes is injected.
To achieve the object, a second ferrule according to the present invention comprises plural groups of fiber holes for insertion of optical fibers formed at predetermined intervals, each group having a plurality of fiber holes. Each fiber hole has a guide hole portion and a minute hole portion whose inside diameter is smaller than that of the guide hole portion.
To achieve the object, a third ferrule according to the present invention, comprises plural groups of fiber holes for insertion of optical fibers formed at predetermined intervals, each group having a plurality of fiber holes. Each fiber hole has a guide hole portion and a minute hole portion whose inside diameter is smaller than that of the guide hole portion. The guide hole portion has a taper portion formed on a minute hole portion side in such a way that the taper portion is tapered toward the minute hole portion and has a length Lt set to 1xe2x89xa7Lt/Lgxe2x89xa7⅓ where Lg is a total length of the guide hole portion.
To achieve the object, a fourth ferrule according to the present invention, comprises plural groups of fiber holes for insertion of optical fibers formed at predetermined intervals, each group having a plurality of fiber holes. Each fiber hole has a guide hole portion and a minute hole portion whose inside diameter is smaller than that of the guide hole portion. The guide hole portion is formed in such a way that the inside diameter thereof becomes smaller in a stepwise manner toward the minute hole portion.
To achieve the object, a fifth ferrule according to the present invention, comprises plural groups of fiber holes for insertion of optical fibers formed at predetermined intervals, each group having a plurality of fiber holes. Each fiber hole has a guide hole portion and a minute hole portion whose inside diameter is smaller than that of the guide hole portion. The guide hole portion is formed in such a way that the inside diameter thereof becomes smaller continuously toward the minute hole portion.
The above and other objects of the present invention and the features and advantages thereof will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings.